Electronic Circuit Analysis using LTSpice XVII Simulator

A Practical Guide for Beginners

Pooja Mohindru, Pankaj Mohindru

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000428483
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This text discusses simulation process for circuits including clamper, voltage and current divider, transformer modeling, transistor as an amplifier, transistor as a switch, MOSFET modeling, RC and LC filters, step and impulse response to RL and RC circuits, amplitude modulator in a step-by-step manner for more clarity and understanding to the readers.

It covers electronic circuits like rectifiers, RC filters, transistor as an amplifier, operational amplifiers, pulse response to a series RC circuit, time domain simulation with a triangular input signal, and modulation in detail. The text presents issues that occur in practical implementation of various electronic circuits and assist the readers in finding solutions to those issues using the software.

Aimed at undergraduate, graduate students, and academic researchers in the areas including electrical and electronics and communications engineering, this book:

• Discusses simulation of analog circuits and their behavior for different parameters.

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• Covers AC/DC circuit modeling using regular and parametric sweep methods.

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• The theory will be augmented with practical electrical circuit examples that will help readers to better understand the topic.

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• Discusses circuits like rectifiers, RC filters, transistor as an amplifier, and operational amplifiers in detail.

1 Introducing LTspice XVII Circuit Simulator

1.1 Introduction

LTspice is a high-performance and easy-to-use circuit simulator based on the SPICE (Simulation Program with Integrated Circuit Emphasis) software. Initially, the general-purpose simulator SPICE was developed at the Electronics Research Laboratory of the University of California, Berkeley (1975) for modeling, analyzing, and displaying electronic (specifically analog) circuits’ behavior. LTspice XVII (the latest version) software package is an excellent schematic-driven circuit simulation program that uses SPICE algorithms to run industry-standard semiconductor and behavioral model simulations very fast. The schematic is a user-friendly interface that allows the user to build circuits (with standard component symbols or models) that can be seen on the screen directly so that they can easily understand them and simulate them without employing the circuit defining SPICE data statements with a specific format or syntax. The schematic capture program transforms the schematic diagram into a netlist which can be easily understood by SPICE. The generated netlist for a particular circuit can be further saved and used in a subsequent analysis of the same circuit.

A digital (simple logic gate) simulation capability is its added feature. A set of wide-ranging enhancements is included, such as parallel processing, dynamic assembly, and object code generation in the SPARSE matrix solver to make LTspice XVII (an enhanced SPICE type analog electronic circuit simulator) the industry unmatched analog simulator.

LTspice XVII has a wide-ranging library of electronic and electrical component models for resistors, capacitors, inductors, diodes, OP-Amps, and transistors which can be placed and connected on the schematic with a mouse to build the desired circuit diagram. The user needs only to enter specific numeric values (variables/expressions should be entered using the simulator valid syntax) in a list of the parameter values provided for the device models stored internally so that the models can perform their intended operation. It provides a waveform viewer for visualizing simulation results. All these features of the simulator make the use of a SPICE program much easier and accessible task for the users. Also, LTspice XVII can include SPICE models of complex analog components like op-amps, voltage regulators, and timers into the circuit.

The schematic is a graphical interface to the circuit netlist generation, that is, the simulator interprets the circuit entered graphically on the schematic by a text netlist generated in the background. The netlist consists of a list of the circuit elements and their nodes, model definitions, and other SPICE commands. LTspice XVII saves schematic drafts with a file name extension of .asc. When a circuit drawn on the schematic is simulated, the netlist information is extracted from the schematic graphical information to a file with the same name as the schematic but with a file extension of .net.

Thus, it is a widely circulated and used simulation software in several areas, which include radio frequency electronics, power electronics, audio electronics, digital electronics, mechanics, physics, and other disciplines. Even though it is freely available, the simulator is not constrained to have bounded capabilities (which imply there is no limit to nodes, components, and sub-circuits), and thus outperforms many simulation solutions in the market.

1.1.1 Need for Electronic Circuits Computer Simulator

It is extensively significant to use SPICE simulators for testing before constructing a new circuit in hardware because simulating and analyzing the designed circuit using the software is easier, time-saving, and less expensive.

Testing with SPICE simulators reduces the wastage of hardware resources. This is because hardware implementation is executed only when accurate simulation results are obtained. On the other hand, when a circuit is tested after fabricating it on a printed circuit board (PCB) and desired results are not achieved, components can be damaged while taking them out of the real circuits. Also, re-soldering may affect the performance of the circuit.

Again, simulation using the software takes much lesser time as is consumed in analyzing the circuits’ responses theoretically.

It is pretty easy to draw and configure a circuit in the software and probing various points to examine the waveforms.

The users can employ the software as a starting point for the development and modification of their designs.

It is possible to test a new thought/idea without a soldering iron.

An existing idea can be easily modified and tested without a real PCB.

1.1.2 Advantages

1. It is free and provides unlimited circuit sizes.
2. It allows adding new models and changing the simulator’s behavior easily.
3. It saves time by eliminating the need of solving the values of voltage, current, and power of any component in a circuit manually.
4. It allows changing the values of components in a circuit so that the circuit can be tested easily before selecting values of components to construct the circuit in hardware.
5. Tells the feasibility of the circuit.
6. LTspice enables the users to iterate their designs in minimal time by doing successive simulations so that we can explore the circuit limitations and performance boundaries of the design with slight adjustments. Further, the SPICE simulation allows interactive measurements of currents, voltages, and power that are almost not possible to compute theoretically or any other way.
7. SPICE simulators are the only way to check the circuits’ behavior prior to integration onto a chip.

As compared to LTspice XVII, PSpice and Electronic Workbench are better at mixed analog/digital circuits.

1.1.3 Hardware Necessities

LTspice XVII runs on 32-bit or 64-bit editions of Windows 7, 8, 8.1, 10, Windows XP, and MacOS 10.9+. As a simulation may generate many megabytes of data in a few minutes, it is endorsed to have free hard disk space (>10 GB) and a large amount of RAM (>1 GB). Fundamentally, the program can run on any PC with Windows 98 or above, but the simulation may not finish if there is not enough hard disk space.

1.2 LTspice XVII Main Interface to Get Started

LTspice XVII is a freeware software for circuit design and simulation using various key circuit simulation and analysis types such as transient (time-dependent), noise, AC, DC, DC transfer function, DC operating point, parametric, temperature sweep, as well as Fourier analysis. It provides the schematic capture (to enter a schematic for an electronic circuit), the waveform viewer (to display the results of a simulation), extensive library of passive devices, unlimited number of nodes, integrated voltage and current probes, FFT function, far-reaching help function, and automatic update. The simulator also allows entering different mathematical expressions in the traced output using the valid functions. It also permits the computation of heat dissipation of the components and the generation of efficiency reports. It permits fast simulation of switching mode power supplies and also provides advanced analysis and simulation options. It contains over 200 Op-Amp models, transistor models, MOSFET models, etc. LTspice XVII does not generate PCB layouts, but netlists can be exported to PCB layout software. Thus, LTspice XVII assists in visualizing a circuits’ responses to arbitrary inputs before they are b...